This invention relates to antistatic agents for synthetic polymer materials and synthetic polymer compositions containing such agents. Synthetic polymer materials are generally hydrophobic and hence tend to become electrostatically charged. These characteristics serve as a big obstacle during their production process as well as when they are used. It is therefore an object of this invention in view of the above to provide antistatic agents for synthetic polymer materials and synthetic polymer compositions containing such agents.
Many kinds of ionic compounds have been used as antistatic agents for synthetic polymer materials. Among these ionic compounds, phosphonium sulfonate has been favorably considered for its superior compatibility with synthetic polymer materials and resistance against heat (as disclosed in Japanese Patent Publications Tokkai Sho-62-230835, Hei-1-14267 and Hei-1-62336 and U.S. Pat. No. 4,943,380). The kinds of phosphonium sulfonate which have been proposed, however, tend to adversely affect the natural hue or transparency of the synthetic polymer materials. Thus, there remains the problem that synthetic polymer compositions containing them are not suited for the production of products which are relatively thick and require a high level of transparency such as optical lenses and covers for lighting products. If the amount of phosphonium sulfonate to be used is reduced in order to limit the effects on the natural hue or transparency, however, the antistatic characteristic of products obtained from such a composition becomes poor especially under a condition of low humidity.